Fuse powder compositions



Patented Jan. 21 1947 UNITED STATES FUSE POWDER COMPOSITIONS Harrison H. Holmes, Woodbury, N. J and Walter E. Lawson, Wilmington, Del., assignors to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware N Drawing. Application January 14, 1944, Serial No. 518,242

4 Claims.

1 This invention relates to a new and improved explosive of the black powder type, and more particularly to such composition adapted for use 4 as a fuse powder under conditions where a fast burning rate is desired.

This application is a continuation-in-part of our copending application Serial No. 422,698, filed December 12, 1941.

With fuse powders, a uniform rate of burning in small diameter cores is an essential. The compositions of powder in common use comprise, generally, intimately incorporated mixtures of potassium nitrate, sulfur, and charcoal, in much the same proportions as these ingredients are present in common black powder compositions. Safety fuse containing a black powder core of small diameter enclosed in a covering of waterproof fabrics ordinarily has a, burning speed of around 90 seconds per yard. Under certain conditions, however, a fuse powder is desirable having an accelerated burning speed above that of standard powders of the prior art.

An object of the present invention is a black powder type composition of a burning speed, when enclosed in small diameter column, greater than has been obtainable heretofore. A further object is such a powder adapted for use in fuse and containing an accelerating ingredient. A still further object is a black powder composition having greater inflammability and an enhanced ability to ignite adjacent explosive charges. Additional objects will be disclosed as the invention is described more in detail hereinafter.

We have found that the foregoing objects are accomplished when we prepare a black powder type composition containing an alkali nitrate, preferably potassium nitrate, sulfur, and a substantial amount of a carbon block of the type produced, by the incomplete combustion of a carbonaceous gaseous fuel, this carbon black constituting at least a partial replacement of charcoal.

Since the carbon black will be of the class comprising blacks prepared by direct contact with a depositing surface of the flame of a carbonaceous gaseous fuel in the presence of a deficiency of oxygen, not all carbon blacks are included within the invention. Charcoal is, of course, outside the scope as this is a charred product retaining the structure of the wood from which it is made.

Boneblack likewise is a destructive distillation product and does not possess the desired properties. The thermal decomposition blacks, the so-called thermatomic carbons, which are produced simply by the thermal decomposition of natural gas out of contact with air, are also not included. It will be apparent that lampblack is outside the scope of the invention, as this is prepared by the incomplete combustion of oils, tars or resins.

The carbon blacks that function according to the invention will include the so-called channel blacks produced by the incomplete combustion of natural gas or other gaseous fuel, where the flames impinge on metal surfaces or channels, on which the black is deposited and from which it is subsequently removed by scraping. Acetylene blacks produced by the incomplete combustion of acetylene will likewise be included. Blacks of this type are used in large quantities as rubber reinforcements, in printing inks. pigments, etc.

Carbon blacks produced by the incomplete combustion of gaseous carbonaceous fuels have properties that distinguish them from other solid carbon products. They are characterized, for example, by relatively high absorptive power for liquids and gases. One way of characterizing such carbon blacks is by their oil absorptive values, and we find a satisfactory evaluation to be in terms of cc. of refined linseed oil retained by grams of the black. A carbon black which gave very satisfactory results in accelerating the burning of fuse powder had an oil absorption value of 600 cc. per 100 g. carbon. This was a channel process gas black. Other satisfactory carbon blacks had absorption values between and 350 cc. In contrast to these, a thermatomic carbon, a carbon black made by the thermal decomposition of natural gas, had an oil absorption Value of 32-33 cc. per 100 g. carbon. This latter type of carbon actually functioned as a retardant for the fuse powder. We find, in general, that carbon blacks for application in accordance with our invention should have oil absorption values of over 100 cc. In addition to the absorption value of 600 cc. cited above for the first of the abovementioned carbon blacks, this material had the following properties:

By way of illustration of the effectiveness of our invention, the following specific embodiments will serve as examples. The black powder formulas, as indicated below, were prepared and tested for burning speed.

Potassium nitrate 74.0 74.0 74.0 Sulfur 9. 5 9. 5 5. 0 Charcoal 16. 5

Carbon black Burning speed, see/yd In the foregoing tabulation, the carbon black used in B and C was of the type specified for this invention. The burning speed, expressed in the number of seconds required for the combustion of one yard of powder, was determined under the following conditions. The powder to be tested was poured into a length of lead tubing having an outside diameter of 0.260". After the powder had been settled, the lead tubing was closed at the ends and by passage through a series of grooves of decreasing size was so reduced that the outside diameter became approximately 0.158". The burning time was then determined on oneyard samples of the powder column in the fuse of reduced diameter.

It will be noted that fuse containing a powder according to our invention burned at a speed of about 46 seconds per yard. No previous powder has been known which had a speed such that it would burn in less than 70 seconds, and the standard fuse has a speed of about 75 seconds. Preferably we maintain a content of our special .carbon black in the powder of between 5% and 25%. While ordinarily we replace all the charcoal in the black powder by carbon black, we may find it desirable at times to make only a partial replacement, though our invention contemplates the use of carbon black in the amount of at least 50% of the carbonaceous material present.

The fast-burning powder of our invention will possess superior utility in a number of respects. It will prove advantageous, for example, for use in electrical circuits where a combustible element is desired to indicate the blowing of an electric fuse. The fast-burning fuse powder likewise possesses superior properties with respect. to ignition of adjacent exposives. It is more readily ignited than previously used compositions, and will likewise be of value in many cases where certainty of ignition in explosive circuits is essential.

As evidence of the higher degree of inflammability of fuse powder in accordance with our invention, samples of this were tested in comparisonwith standard fuse powder containing sporting charcoal. Using a testing method in which small samples of the powder were placed in back of a slot opening, with a compound pendulum 4 having an adjustable opening swinging past and in front of said slot, a standard hydrogen flame was caused to play on the location of the slot. The inflammability was determined by dividing by the time in seconds necessary for application of the flame and ignition of the powder. Using such a method, the inflammability of powder according to our invention was found to be over 11,500, as against 2,900 for standard fuse powder.

In the foregoing description, and in the claims following it will be understood that the term black powder or modified black powder is used to designate all compositions comprising intimate blends of an alkali metal nitrate, particularly potassium and sodium nitrates, sulfur, and carbon. Various other modifying ingredients may be present in small amounts, however. It will be understood, therefore, that many minor changes in compositions may be made without departing from the spirit of the invention. We intend to be limited only by the following patent claims.

We claim:

1. A modified black powder composition containing between 5% and 25% of a carbon black prepared by the incomplete combustion of a carbonaceous gaseous fuel.

2. A black powder type composition comprising an alkali metal nitrate, sulfur, and a carbon black prepared by direct contact with a depositing sur face of the flame of a carbonaceous gaseous fuel.

3. A modified black powder composition comprising potassium nitrate, sulfur, and a carbon black prepared by direct contact with a depositing surface of the flame of a carbonaceous gaseous fuel.

4. A modified black powder composition characterized by its rapid rate of burning and comprising potassium nitrate, sulfur and between 5% and 25% of a carbon black prepared by direct contact with a depositing surface of the flame of a carbonaceous gaseous fuel.

HARRISON H. HOLMES. WALTER E. LAWSON. 

